Oh how I hate CAPTCHA, the popular little form spam preventer. While good in theory, CAPTCHA punishes a user that's probably trying to either register with a website or contact the people behind it—neither of which do you ever want to make more difficult.

As an alternative to CAPTCHA, why not ask your user a super simple question in plain text that only a human could answer? Like, "Are we on planet Earth?" or "Are you using a computer?" or even "Are you human?"